[Python-Dev] PEP 418: rename time.monotonic() to time.steady()? (original) (raw)

Cameron Simpson cs at zip.com.au
Tue Apr 3 23:53:51 CEST 2012

On 03Apr2012 13:26, Victor Stinner <victor.stinner at gmail.com> wrote: | I would to rename time.monotonic() to time.steady() in the PEP 418 for | the following reasons: || - time.steady() may fallback to the system clock which is not | monotonic, it's strange to have to check for | time.getclockinfo('monotonic')['ismonotonic'] | - time.steady() uses GetTickCount() instead of | QueryPerformanceCounter() whereas both are monotonic, but | QueryPerformanceCounter() is not steady || Python steady clock will be different than the C++ definition. || You may argue that time.steady() is not always steady: it may fallback | to the system clock which is adjusted by NTP and can jump | backward/forward with a delta greater than 1 hour.

An HOUR ?!?!?

I have to say I'm -100 on any proposal where time.monotonic() returns non-monotonic time and likewise for time.steady() returning unsteady time.

| In practice, there | is only one operating system that does not provide a monotonic clock: | GNU/Hurd.

I'd have thought practically any early UNIX falls into this category. And any number of other niche things. (Yes I know Python doesn't run on everything anyway.) Are we only considering Linux/Mac/Windows, and only recent versions of those?

What's the status of Java and Jython?

| I hesitate to add "issteady" to time.getclockinfo(), but a boolean | is not very useful, it would be better to have a number. || Arguments for time.monotonic() name: || - Users are looking for the "monotonic" name | - Most of the time, time.monotonic() is a monotonic clock

Again, here, I'm -100 on "most". If I ask for monotonic, it is because I need one. Given me monotonic or give me death! (Well, an exception or at any rate something unusable like None.)

[...] | PS: I already changed time.monotonic() to time.steady() in the PEP :-p

Sigh. They're different things! For all that "steady" is a slightly vague term, steady and hires and monotonic are independent concepts. Of course a lot of high quality clocks will embody hires and ideally steady or monotonic.

This kind of offer-just-one-thing embedded policy is why I feel the API needs more user control and a polciy free interface, with montonic() et al providing handy prepackaged policy for the common uses.

If you can provide monotonic (for example, on Linux as you outline), which not offer it? Offering steady() provides no way for the user to ask for higher guarentees.

Cheers,

Cameron Simpson <cs at zip.com.au> DoD#743 http://www.cskk.ezoshosting.com/cs/

But in our enthusiasm, we could not resist a radical overhaul of the system, in which all of its major weaknesses have been exposed, analyzed, and replaced with new weaknesses. - Bruce Leverett

More information about the Python-Dev mailing list